This invention relates to herbicidal compositions. Of particular concern are herbicidal compositions containing two kinds of compounds as active ingredients which possess remarkable synergistic effects that cannot be expected by application of compositions containing only one or the other type of compound.
In recent years, many excellent herbicides have been developed and employed to provide easy and rational control of annual weeds in paddy fields. A problem has arisen due to perennial weeds, previously occurring only locally, but of late spreading extensively along with the annual weeds. Measures for combatting this are eagerly being sought. Several factors can be cited to account for the propagation of such perennials, such as changes in cultivation and seeding methods and inadequate control of the cultivations. The principal factor apparently is the continued employment, for many consecutive years, of narrow-spectrum herbicides effective against annuals but ineffective with perennials. Under the circumstances, a great need exists for the development of broad-spectrum herbicides capable of combatting perennials as effectively as annuals.
Japanese patent publication No. 42853/77 discloses a plant growth regulator containing 5-(N-phenylcarbamoylamino)-1,2,3-thiadiazole. This compound has the effect of inhibiting weeds. Tests on the herbicidal properties of this regulator reveal that it has the effect of controlling the growth of annual broad-leaved weeds, annual cyperaceae weeds, and perennial weeds such as Scirpus erectus when applied during the pre-germination period or in the early stage of germination of weeds in paddy fields, but that it displays inferior results with Barnyardgrass and Monochria Vaginalis, which are strong harmful weeds. Additional disadvantages include a narrow herbicidal spectrum and narrow period of application.
The use in combination of various herbicides has been attempted, but it is widely recognized that in almost all instances the effect is a mere sum of the results attainable by the respective herbicides used alone, or, alternatively, that the effects of the respective herbicides compensate each other.